Some engines, known as a variable displacement engines (VDE), may be configured to operate with a variable number of active and deactivated cylinders to increase fuel economy. Therein, a portion of the engine's cylinders may be disabled during selected conditions defined by parameters such as a speed/load window, as well as various other operating conditions including engine temperature. An engine control system may disable a selected group of cylinders, such as a bank of cylinders, through the control of a plurality of cylinder valve deactivators that affect the operation of the cylinder's intake and exhaust valves, through the control of a plurality of selectively deactivatable fuel injectors that affect cylinder fueling, and/or through the control of the ignition system to selectively control (e.g., withhold) spark to deactivatable cylinders. By deactivating engine cylinders at low speeds/light loads, associated pumping losses can be minimized, and engine efficiency is increased.
However, noise, vibration, and harshness (NVH) may be caused during engine transitions between a VDE state where one or more cylinders are deactivated, and a non-VDE state where all cylinders are active. Specifically, the engine's crankshaft and firing order are defined to reduce NVH when all cylinders are active. Engine torque production and engine speed may be smoothest (e.g., producing least variation from desired engine torque and desired engine speed) when the engine is operated with its full complement of cylinders. In the VDE state, engine torque variation and engine speed variation from desired values may increase because of longer intervals between combustion events. As a result, NVH from the engine during a VDE state, as observed by vehicle occupants, may increase. If the engine is operated with higher levels of noise and vibration, vehicle occupants may find riding in the vehicle objectionable. Thus, it may be difficult to provide higher levels of fuel efficiency without degrading the driving experience.
One example approach for reducing the VDE associated NVH is shown by Rollinger et al. in U.S. Pat. No. 10,006,379. Therein, a larger number of VDE states are enabled when an estimate of road roughness is elevated. Consequently, an engine can be operated in the VDE mode when the NVH associated with the VDE transition can be masked by road roughness and vehicle occupants are less likely to notice the NVH.
However the inventors herein have identified potential issues with such an approach. As one example, rough roads may be far and few in between. As a result, relying on road roughness may result in limited opportunities to enable VDE operation.
The inventors have recognized that there may be other conditions where a vehicle driver is distracted that can be leveraged for providing more opportunities for VDE operation. For example, during conditions when a driver is engaged in in-cabin conversation (or otherwise distracted), or when cabin speakers are operating at an elevated volume, the driver may not notice the NVH. Likewise, the NVH may not be perceived when ambient noise around the car is elevated.
Further still, if the vehicle operator is a transient driver, such as may occur due to car sharing, the driver may not be as concerned about the vehicle's NVH as long as the vehicle is performing the main task of transporting the driver to the desired location. The same may be true for a vehicle occupant if the vehicle is a driverless autonomous vehicle. During such conditions, cylinder deactivation does not need to be limited on account of driving experience being affected by NVH.
Thus in one example, NVH related to cylinder deactivation may be better balanced with fuel economy by a method comprising: initiating a transition between operating an engine with more cylinders active to operating with fewer cylinders active in response to one or more of audio and video feed captured at the vehicle.
As an example, various vehicle sensors may be used to capture in-vehicle as well as ambient vehicle noise. Likewise, vehicle cameras may be used to monitor occupant behavior. The audio and video feeds may be analyzed, for example using voice-recognition software to identify if the driver is engaged in conversation, and using image analysis (such as eye movement, hand movement, etc.) to identify if the driver is exhibiting distracted behavior. A vehicle controller may schedule a VDE transition (from a non-VDE mode to a VDE mode, or vice versa) to occur while the driver is talking or distracted, as inferred based on the audio and/or video feed captured inside (or outside) the vehicle. Furthermore, VDE may be controlled based on engine operating conditions, and with reduced constraints regarding driver dissatisfaction, during conditions when the vehicle is used for car sharing or when the vehicle is driven autonomously. Consequently, it may be possible to provide the technical result of operating an engine cylinder in a cylinder deactivation mode at a time when vehicle occupants are not likely to notice the additional engine noise and vibration.
The present description may provide several advantages. In particular, the approach may provide improved vehicle fuel economy by enabling cylinder deactivation to be applied over a larger portion of a drive cycle. In addition, the approach may reduce the possibility of disturbing occupants of a vehicle while cylinders are deactivated or while they are transitioned between active and deactivated states. Further, the approach may enable cylinder deactivation responsive to audio and video feed captured inside and outside the vehicle so that fuel economy may be increased while vehicle occupants are less susceptible to noise and vibration that may be related to deactivating engine cylinders.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.